First of all, an outline of the processes in copper smelting will be explained. Ore dug out from a mine is called “crude ore”, and since it contains large amount of worthless materials (so called gangues) besides useful minerals, gangues are removed from the crude ore as tailings by a process called “concentration”, and the concentrates of high-grade obtained thereby are applied to smelting. The difference in physical or physicochemical property of minerals such as density, hardness, magnetism, permittivity, wettability is employed in the concentration processes.
Concentrates obtained by concentration are thermally dried for the purpose of reducing heat energy required in smelting processes, making easier to handle minerals in case of supplying and transporting them to furnaces, and also avoiding decrease in responsiveness due to moisture. Drying process is implemented, for example, by a rotary drier such as rotary kiln comprising a furnace formed in a slightly sloping long cylindrical shape.
Concentrates obtained are supplied to a flash furnace with the oxygen enriched air or hot air of high temperature simultaneously to induce chemical reaction, and separated to matte and slag by the difference in specific gravity. The flash furnace 1 employed in the process is comprised of a reaction shaft 3, a settler 5 and an uptake 7 as shown in FIG. 7, and the said reaction shaft 3 is provided with 1˜3 concentrate burners 9, 9. The concentrates are blown into the furnace via the concentrate burners 9, 9. The flash furnace is characterized to be lower in specific fuel consumption than other means since it utilizes heat produced by oxidation reaction of the concentrates. However, in case the heat produced by oxidation reaction is not enough, auxiliary combustions from the concentrate burners 9, 9 using fuel oil and such can be implemented.
Matte in a molten state is then drained from matte tapholes 2a, 2a plurally installed near the bottom of the flash furnace 1. 60% to 70% of copper is normally included in the matte obtained in this process. On the other hand, about 1% of copper is included in the slag, so it is drained from a slag taphole 2b perforated at the lower part of the uptake 7 to be sent to a slag cleaning furnace 1a and cleaned. Then the copper obtained is recovered in a form of matte and combined to the matte obtained from the flash furnace 1 to be processed in a converter. A more high-grade electrolytic copper will then be manufactured by electrolytic refining.
Today, in copper smelting industry employing flash furnaces, a melting operation is becoming high-load, with the annual processing quantity per furnace which used to be 300,000 tons, now increasing to its doubled quantity. Since the amount of oxygen enriched air as well as the temperature within the furnace become more severe in high-load operations, refractory materials such as heatproof bricks within the furnace will wear out more quickly. Particularly, heat load to the lower part of the shaft and the connection between the shaft and the settler will be increased significantly. Due to such reasons, there was a need to replace the refractory material within the furnace more frequently, and in the aim of stopping the progression of refractory deterioration, a structure for cooling the furnace body has been proposed (for example in JP Patent Publication No. 2006-71212).
[Patent Reference 1] JP Patent Publication No. 2006-71212 Official Gazette